[BUG] install-strategy=linked: napi-postinstall cannot resolve an installed optional native binding #9620

Part of #9608.

Is there an existing issue for this?

• I have searched the existing issues

This issue exists in the latest npm version

• I am using the latest npm

This is not just a request to bump a dependency for a CVE

• This is not solely a request to bump a dependency for a CVE

Current Behavior

Under install-strategy=linked, an optional native binding is installed and symlinked in the store and resolves at runtime, but napi-postinstall run from a consumer package's own store directory reports the binding missing (Failed to find package "@unrs/resolver-binding-darwin-arm64") and tries to re-install it. It is non-fatal only because the public registry serves the binding tarball; on a restricted/proxy registry the re-download fails. The hoisted strategy places the binding at a reachable top-level location and the same check passes silently.

Expected Behavior

A consumer package's installed optional native binding should be resolvable from napi-postinstall's vantage point under the linked strategy, without triggering a redundant re-download, matching the hoisted strategy.

Steps To Reproduce

cd "$(mktemp -d)"
echo 'install-strategy=linked' > .npmrc
cat > package.json <<'EOF'
{ "name": "napi", "version": "1.0.0",
  "dependencies": { "unrs-resolver": "1.11.1" },
  "allowScripts": { "unrs-resolver": true, "napi-postinstall": true } }
EOF
npm install >/dev/null
cd node_modules/.store/unrs-resolver@*/node_modules/unrs-resolver
node ../.bin/napi-postinstall unrs-resolver 1.11.1 check
#   linked:  [napi-postinstall] Failed to find package "@unrs/resolver-binding-darwin-arm64" ... Trying to install
#   (require.resolve from the same dir finds the binding; hoisted's check passes silently)

Environment

• npm: 12.0.0-pre.1 (latest)
• Node.js: v24.17.0
• OS Name: macOS (Darwin 25.5.0)
• System Model Name: MacBook (arm64)
• npm config:

install-strategy=linked